講義スライド3

Japanese Young Physicist Summer School
Tokyo, August 19 – 24, 2008
Heavy Element Synthesis
In Supernovae
Taka Kajino
National Astronomical Observatory
Department of Astronomy, University of Tokyo
1
!!!!!"#$%&'()*+,!!()*./012(3456789:;<=;>?@AB)*
CDE'+FG1!HCDIJK
CDEL>MNO@0BPQR137 +/- 2 SIR --- Model dependent!
!!!T!We donUV know the true nature of DARK MATTER nor DARK ENERGY.
WCDIXY (Nucleo-cosmochronololy)
!!!232ThZ[\]140.5SI^_238UZ[\]45.7SI^6`]aXbc@def_
!!`]bc+IJ6PQRgh@01_ijkCDIJ+lmn6PQoBR
!!CDEL>MNO@pqrstufv3R
!!`])*56PQoBwxyzBR
!!!!!!!!!!!!"#$%&_()*{|}~•_€•N9:‚ƒ„…†+‡ˆ‰R
!!!!!!!!!!!!CD+‰YŠ‰_()*+,-E'+FG1R
2
Solar System Abundance
BIG-BANG
Constrains Cosmology !
Supernova, prompt or delayed ?
Neutron Star Merger ?
Gamma-Ray Burst ?
STARS
!!
!!!
R S!ZN=50)
!!!
R SZN=82)
COSMIC-RAYS
R-process elements,
UNKNOWN!ORIGIN ?
AGB STARS
!!!
R !
SZN=126)
++
+
P
Actinide
232Th
238U
(14.05Gy)
(4.47 Gy)
Supernova-! Process ?
3
‹W!!!!!!
!!!!!!!!!
SW
!!
!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!
RW
4
Very Rapid Neutron-Capture Process
(! = 14.05 Gy)
232
90
153
63
Z
Th
142
Pt, Au
Eu
A=195
90
Pb
I, Xe
Chart
r-p
ss
ro c e
p a th
A=130
Se, Br, Kr
A=80
3-rd peak
Ba
Sr, Y, Zr
2-nd peak
Fe-Co-Ni
(stable)
1-st peak
No structure
These ate not “seeds” because r-process is
a primary process starting from prorons & neutrons !
N
5
We detected "’s, then NEUTRON STAR once formed !
SN1987A
Can core-collapse supernova produce R-PROCESS elements
6
232
like Th(!1/2=14.05Gy) which is an celestial cosmic clock ?
Subaru Telescope
OBSEVES Extremely MetalDeficient Stars
[Fe/H]=0
SOLAR
[Fe/H]<-3
!Th
II HD6268
7
Honda, Aoki, Kajino et al.
!!(SUBARU/HDS Collaboration),
2004, ApJS 152, 113; 2004, ApJ 607, 474
solar s-ratio
0
+ AGB
[Fe/H]
SN II
[Ba/Eu]
[Ba/Fe]
SUBARU Telescope HDS
0
solar r-ratio
SN I + II
[Eu/Fe]
R-process elements from Type II SNe !
Large abundance scatter at [Fe/H]<-2
is an evidence for INDIVIDUAL
supernova episode.
0
Lack due to
obs. limit.
Early Galaxy
[Fe/H] = log(NFe/NH) - log(NFe/NH)
Only Core-Collapse TYPE II SUPERNOVAE are the likely astrophysical
sites of the R-Process !
8
UNIVERSAL SCALING
OF R-PROCESS ABUNDANCES
Ba
SOLAR
C. Sneden et al. (1996 – 2005)
METAL-POOR
STARS
Eu
HD 115444
CS 22892-052
BD +173248
R-Element Abundance Pattern is:
METAL-INDEPENDENT !
UNIVERSAL !
9
Cosmic Clock
Collapse of the Core
Prompt core bounce
E(iron core) ~ GM2/r ~ 1051 erg
E(neutron star) ~ GM2/r ~ 1053 erg
E(neutron star) - E(iron core) ~ 1053 erg
99% is emitted as neutrinos!
E(shock) ~ 1051 erg
1% is kinetic energy!
Usually the shock is absorbed by
dissociating the iron core.
Neutrino-heated explosion
DELAYED SUPERNOVA10
Steps to a Core Collapse Supernova
•
Stars with M ~ 10 - 40 M! build up an Fe/Ni core.
Maximum core size Mch = 5 Ye2 M! ~ 1.3 M! (Electron Capture).
•
Collapse Separates,
inner homologous (v #r) core = 1.1 M! .
outer slowly collapsing core = 0.2 M! .
The central density increases and reaches nuclear matter density,
$nucl ~ 2x1014 g cm-3
(Nuclear EOS).
•
An outward moving shock develops due to nuclear saturation.
•
The shock dissociates the outer iron core into free nucleons.
•
Neutrinos scatter off the heated material behind the shock and
deposit energy into p, n, and e+e-.
•
A high entropy heated region forms and begins to lift the outer layers
11
of the star (neutrino-driven wind).
"#$%&+Œn•Ž••‘•’N•“? !”•;–Z—:˜™š^
10 km
300 km
12
Before
Explosion
28Si
Fe
Co
Ni
SN1987A MODEL: Where occurs r-process ?
After
Explosion
?
?
Ejected Fe-Co-Ni are explosively
reproduced in Si-burning !
13
General Relativistic Models of "-Driven Winds
Otsuki, Tagoshi, Kajino and Wanajo 2000, ApJ 533, 424
14
Nucleosynthesis + Diffusion Equation for Z < 100 (~3000 species)
Given T & $ :
Nuclear
Reactions
%-decays
Diffusion
Thermonuclear Reaction Rate
Boltzmann average
Cross Section
15
t=0
Pb
SUPERNOVA R-PROCESS
!t = 0
!Neutrino-driven wind forms
!right after SN core collapse.
! n+p+&
Z
Otsuki, Tagoshi, Kajino & Wanajo
2000, ApJ 533, 424
Wanajo, Kajino, Mathews & Otsuki
2001, ApJ 554, 578
›
Fe
›
N
Pb208
›
Fe56
›
!t = 18 ms
Seeds form.
Exotic neutron-rich
Ni78
78Ni
!t = 568 ms – 1 s
Heavy r-elements synthesize.
Pb
›
Fe
›
16
Very Rapid Neutron-Capture Process
(! = 14.05 Gy)
232
90
153
63
Z
Th
142
Pt, Au
Eu
A=195
90
Pb
I, Xe
Chart
r-p
ss
ro c e
p a th
A=130
Se, Br, Kr
A=80
3-rd peak
Ba
Sr, Y, Zr
2-nd peak
Fe-Co-Ni
(stable)
1-st peak
No structure
These ate not “seeds” because r-process is
a primary process starting from prorons & neutrons !
N
17
RIKEN-RIBF New Ring Cyclotron (2007)
132Sn
2nd r-peak element !
78Ni,
expected !
seed element for
r-process !
18
œ•žZŸ> ¡:N^¢(xv
Z£^W¤¥¦§¨©
REACTION NETWORK
BIG-BANG
NUCLEOSYNTHESIS
R-PROCESS
NUCLEOSYNTHESIS
)*{|@ª«B¬-+
®¯¦Q5°@©
19
Reaction Sensitivity
Sasaqui, Kajino, Mathews, Otsuki & Nakamura
!!!!!!!!! Astrophys. J. (2005), submitted.
20
Identified Important Reaction Flow Paths
Woosley & Hoffman
(1992)
(3)
Sasaqui, Kajino, Mathews,
Otsuki & Nakamura
ApJ (2005), submitted.
(1)
(2)
Terasawa, Sumiyoshi, Kajino,
Mathews & Tanihata
ApJ 562 (2001) 470.
21
(1) &(&n,')9Be(&,n)12C!!!35%(1()
22
R-Process Sensitivity to Individual Reaction
Factor of 2 change of &(&n,')9Be reaction rate
About factor 50 change in r-element yields !
(slowly expanding "-wind model)
± &(&n,')9Be²
~ 50
± &(&n,')9Be²x 2
23
Nucleosynthesis proceeds: NSE ³ "-process ³ r-process
Rich Neutron
1. High Entropy/beryon :-- primary process
2. Low initial-Ye :-- neutron-richness
T9 = T / 109
3. Short #dyn :-- high neutron-to-seed
n+p
+4He
Neutron/Seed
n + p + 4He ³ seeds
n + seeds ³ r-elements
r-process
#dyn
time (sec)
freezeout
24
25
Neutron-Capture Cross Section ((18C(n,')19C) [µb]
Experiment (Coulomb Diss. + Detail. Balance)
Nakamura et al. PRL83 (1999) 1112.
100
Hausser-Feshbach Estimate
26
Abundance Evolution of Carbon Isotopes
Abundance YA
16C(&,n)19O
Sasaqui et al. (2005)
18C(&,n)21O
100
19C
Time (sec)
27
New Waiting Points in Light-Mass Nuclei
130In
HEAVY
LIGHT
%
129Cd
130Cd
131Cd
)
N = 82
(&,n
WAITING
%
Both (n,') and (&,n) are
FAST enough so that
18C waits for %-decay.
NEW WAITING
28
(2) &(t,')7Li!! 30%(1()
R-PROCESS
& BIG-BANG
Kajino et al. (2005)
29 !
REMOVING UNCERTAINTY
30%(1
(3) 7Li(n,')8Li(&,n)11B
Factor 2 (1()
H. Ishiyama et al. AIP Conf. Proc. 704 (2004) 453.
THEORY, unfinished.
Yamamoto, Kubo, Ogawa & Kajino
11
11
Bg + several
B* (EXCLUSIVE EXP.)
Excited 11B*
R-PROCESS
!!!!´
INHOMOGENEOUS
BIG-BANG
Ground 11Bg
30
SENSITIVITY of Relevant Reactions to R-Process
!!!
Sasaqui, Kajino, Mathews, Otsuki & Nakamura, ApJ (2005) submitted.
!Otsuki, Tagoshi, Kajino & Wanajo, ApJ 533 (2000), 424.
Y0,r+)Yr = Y0,r {1+2(}&
(1) &(&n,')9Be
1( = 35%
(Y0+)Y)/Y0 = 0.35 µ 11.2
(2) &(t,')7Li
1( = 30%
0.27 µ 13.2
(3)(4) 7Li (n,')8Li(&,n)11B
1( = 35%, x2
*(Th/Eu)=0.7
0.79 µ 1.7
*TG = 7.2 Gy !
31
SENSITIVITY of 232Th & 235,238U to 18C(&,n)21O
Sasaqui, Kajino, Mathews, Otsuki & Nakamura, ApJ (2005) submitted.
13.7 Gy
Th/Eu-Chronometer
6.47 Gy
32
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33